The present invention relates to a smectic liquid crystal composition for a recording display medium, which is responsive to an electric field or heat to display or record various types of information, a recording display medium comprising, a smectic (liquid crystal)/polymer composite film using the liquid crystal composition, and use thereof. The recording display medium can be widely used as rewritable cards, displays, and other recording display media.
At the present time, liquid crystals are applied as a display material to a variety of equipment and have been put to practical use in watches, clocks, pocket calculators, miniature televisions and the like. A nematic liquid crystal has been used for this purpose, and TN type and STN type display systems have been adopted.
This type of display device comprises a liquid crystal cell having a transparent electrode, a liquid crystal sealed thereinto, and a polarizing plate provided on both sides of the cell. The use of the polarizing plate results in lowered angle of visibility and lack of brightness, necessitating a backlight having high power consumption. In addition, increasing the display area is difficult due to the necessity of even cell thickness, and there are additional problems such as a complicate, structure and a high production cost.
In recent years, display devices using a (liquid crystal)/polymer composite film, wherein a liquid crystal is present in a polymer matrix, have attracted attention as a liquid crystal display medium which can solve the above problems. Among them, those utilizing a smectic liquid crystal enables the liquid crystal to be maintained aligned even after removal of external energy used for alignment of the liquid crystal and, hence, have such a memory effect that the display can be stored for a long period of time, rendering these display devices useful as recording display media.
Not only a high contrast but also a high performance which causes neither lowering of the contrast nor disappearance of display in low temperature and high temperature regions such as encountered in the use under subzero temperatures at outdoors or within cars under the blazing sun is required of the rewritable recording display medium utilizing the smectic liquid crystal. At the present time, there is no recording display medium satisfactorily meeting this requirement.